Alloy



Patented Sept. 11, 1934 UNITED STATES PATENT OFFICE ALLOY No Drawing. Application September 14, 1933, Serial No. 689,428

2 Claims.

Our invention is directed to an alloy of lead and has for one of its objects the provision of an alloy which .is particularly well adapted for the sheaths of electric power cables, our improved 5 alloy possessing characteristics which are very desirable in suchuse.

The quality of impregnated paper cables for the transmission and distribution of electric power has been greatly improved during the past few years by reason of the quality of the paper and oil used and the manufacturing processes employed. As a result, the number of cable failures due to the insulation has been reduced. On the other hand, an increase in the number of failures assignable to the lead sheath-the protective covering for the insulation-has been noted. This increase in sheath failures is partially due to the higher internal pressures which occur in present day cables as a result of the greater amount of oil employed and partially to the physical characteristics of pure lead. Lead is a comparatively soft, ductile metal, having practically no yield point and consequently, even with moderate stresses, it will stretch. In the case of lead sheath, this means thinning of the lead wall and eventually rupturing of the sheath as it no longeris able to withstand the internal pressures existing in the cable as it heats up due to carrying a power load.

The lead alloy of the present invention is strong and tough, butv not brittle. Its physical properties, such as tensile strength and elongation, show it to be much superior to ordinary lead, in that its tensile strength is much higher and its elongation lower. Where with ordinary lead the yield point is very low, the yield point of our alloy is only slightly less than its ultimatestrength. This is most helpful as it per- -mits of a very much higher internal pressure in a cable without stretching of the sheath. For example, we have noted for the same size sheath and wall thickness an expansion six to eight times as much for ordinary lead as for our alloy. This is due to the remarkable homogeneity of the mixture and small grain or crystal structure. The usual types of alloys of lead, such as tin and lead or antimony and lead, do not act in a similar manner. In fact, one of the objections to the use of such alloys is the ease of segregation of the tin or antimony before sheathing. This does not occurwith the alloy of the present invention. Furthermore, the thorough mixing of the materials ofour alloy aids greatly in obtaining a uniform sheath, thereby improving the stability and strength of the sheath in service.

In addition to all of the foregoing, our alloy not only is superior to ordinary lead as a sheath material in service, but is also a superior metal to run on the lead press. The covering of an electric power cable with a sheath is an inter mittent operation. As the cable advances through the press die block the plastic metal is forced through the die under extremely high pressure. When the supply or charge of lead is exhausted the run is stopped, the press cylinder is refilled and allowed to cool, and then the new charge of metal'is forced through the die as before. At the end of each of these runs there is always some lead known commercially as a slug, left in the press, and the surface of this slug" becomes oxidized in spite of all care exercised to prevent it, so that a homogeneous bond between the fresh charge of metal and the preceding charge is prevented by reason of the presence of this oxide. We have found that the resistance of our alloy to oxidation is very high and hence oxidation of the slug to a detrimental extent does not occur, thereby insuring a homogeneous bond between the fresh metal and that of the preceding charge.

We also find that our alloy is more easily extruded than other alloys of lead, permitting a rate of extrusion almost the equal of pure lead.

' We have noted also that due to its higher resist- Lead 98.85% to 99.75% Antimony 25% to 1% Vanadium .005% to .1-5%

it being understood that in any event the amount of lead employed is farin excess of the antimony and vanadium.

What we claim is:

1. An alloy comprising lead, antimony and vanadium in the proportions of:

Lead 98.85% to 99.75% Antimony .25% to 1% Vanadium .005% to .15%

,2. A lead alloy sheath for electric power cables consisting'of lead, antimony and vanadium in the proportions of:

Lead 98.85% to 99.75% Antimony 25% to 1% Vanadium .005% to .15%

ROBERT J. WISEMAN. BENJAMIN B. REINITZ. 

